Monday 8 February 2021

QRP Labs QCX Mini - Part 3: a portable powerpack

The QCX Mini! An amazingly small and versatile mini CW - only transceiver for amateur radio. Read all about it here:

QRP Labs Kits website

The kit is really nice out of the box, but there's always room for modifications. Some are necessary, some are just nice-to-haves or just plain silly (as always, I'll leave it up to you to categorize this article).

A portable power supply

Having a portable transceiver is nice, but it will not do much good if the battery isn't equally portable. Here's a quick description of my solution to this.

What type of battery to use?

To achieve optimal portability we will need a compact battery pack that is easy to charge and has a good capacity to weight ratio. RC planes and model cars make use of very compact batteries, but these generally require a special charger with balancing connector.

Fortunately battery packs exist with built-in balancing boards. While more expensive, these are much easier to connect and charge. The extra costs are offset by the fact that they can be charged with a normal adapter.

The parts

It's simple really. This is all you need:

I've settled for a 2600mAh Li-Ion battery pack from Ansmann, a German supplier of high quality batteries. I'm sure other suppliers exist, but this one is readily available here in Europe. Why this one? Well, because it includes all this:

  • Balancing logic to properly charge each individual cell
  • Charge controller, to allow charging from a standard Li-ion charge adapter
  • Electronic short-circuit protection, resets automatically after next charge cycle
  • High voltage (overcharge) protection
  • Low voltage (discharge) protection

So, adding a fuse holder, switch and DC socket and some time leads to this:

Perfect! At 100x82x27mm the enclosure is a bit larger than the QCX Mini (but not much) so they can be stacked op top of each other. The battery pack supplies 14.4 Volts and even a bit more when freshly charged,  so if you have a version 1 QCX mini please make sure to apply the regulator mod first!

(Don't know what that is about? Please check this article)

The QCX Mini draws less than 90mA @14.4Volts even with the backlight on, and less than 1A on key down, so 2600mAh will keep the Mini happy for a long time; certainly more than a day of normal use. 

Parts List:

  • Battery pack: Ansmann 4INR19/66 4-cell Li-Ion (Conrad no 2250358)
  • Fuse holder: Conrad no 533769 or equivalent
  • Switch: Conrad no 703486 or equivalent
  • Metal enclosure: EBay 143844704460 (or search for 'Extruded Aluminium Project Box')
  • Charger: 16.8Volt / 1Amp Li-Ion charge adapter (AliExpress, Ebay or local supplier)


Any comments on this article? Need more details? Please drop me a line below!

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